Approximately 53 million people living in the United States have some form of chronic condition or disability, of whom an estimated 15 million adults experience difficulty with walking. Numerous innovative therapies have been developed in the past to assist people in relearning to walk, move and improving their overall health. In this regard, body weight support treadmill training (BWSTT) was developed, that involves patients walking on a treadmill with their body weight partially supported by a body harness to reduce the load each leg must carry while walking. The extent of harness support is progressively decreased as strength and movement control improves. This technique has led to improvements in walking so that patients' outcomes exceed the gains arising from conventional therapy.
BWSTT, however, is not available in many settings because of the costs associated with using two to three therapists or clinicians and/or physical trainers to guide leg and trunk movements during training sessions. Additionally, the assistance can be very physically challenging for clinicians and poses a risk for injury. As a result, facilities and clinicians often settle for traditional over ground gait training therapy, hence preventing many patients from utilizing a promising intervention.
Recently, mechanized gait retraining devices (including robots) have emerged in part to address the challenges associated with BWSTT; however, these devices are primarily used in research-affiliated facilities and larger metropolitan areas. The expense of the devices (approximately $100,000 to $275,000) limits many clinics, hospitals and/or medical centers from purchasing the devices. Hence, individuals receiving care in more rural areas often lack access to a suitable rehabilitative technology.
Persons with disabilities and chronic medical conditions are at greater risk for developing additional medical problems than persons without disabilities, in part due to an inability to exercise at sufficiently challenging levels. Despite the large number of health and fitness centers available in most cities, many persons with activity limitations are unable to use these facilities. Common factors for the non-usage of the available facilities are inaccessible equipment and a lack of staff expertise in how to safely develop and implement a fitness programs for persons with chronic medical conditions. The lack of usable equipment is unfortunate because involvement in moderate levels of sustained exercise helps to prevent or delay the onset of other chronic conditions. Additionally, exercise prevents or reduces further functional declines associated with disuse and inactivity. One example of inadequate equipment is the elliptical trainer (also called a cross-trainer). These elliptical trainers guide the feet along a generally elliptical shaped curve to simulate the motions of walking, jogging and climbing. Numerous elliptical trainers have been disclosed in the patent literature. Rogers, Jr. in U.S. Pat. Nos. 5,527,246, 5,529,555, 5,540,637, 5,549,526, 5,573,480, 5,591,107, 5,593,371, 5,593,372, 5,595,553, 5,611,757, 5,637,058, 5,653,662 and 5,743,834 shows elliptical pedal motion by virtue of various reciprocating members and geared linkage systems. Miller in U.S. Pat. Nos. 5,518,473, 5,562,574, 5,611,756, 5,518,473, 5,562,574, 5,577,985, 5,755,642 and 5,788,609 also shows elliptical pedal motion using reciprocating members and various linkage mechanisms along with oscillating guide links with control links to determine pedal angles. Elliptical trainers in many cases provide inertia that assists in direction change of the pedals, making the exercise smooth and comfortable (see, e.g., U.S. Pat. No. 5,242,343 to Miller; U.S. Pat. No. 5,383,829 to Miller; U.S. Pat. No. 5,518,473 to Miller; U.S. Pat. No. 5,755,642 to Miller; U.S. Pat. No. 5,577,985 to Miller; U.S. Pat. No. 5,611,756 to Miller; U.S. Pat. No. 5,911,649 to Miller; U.S. Pat. No. 6,045,487 to Miller; U.S. Pat. No. 6,398,695 to Miller; U.S. Pat. No. 5,913,751 to Eschenbach; U.S. Pat. No. 5,916,064 to Eschenbach; U.S. Pat. No. 5,921,894 to Eschenbach; U.S. Pat. No. 5,993,359 to Eschenbach; U.S. Pat. No. 6,024,676 to Eschenbach; U.S. Pat. No. 6,042,512 to Eschenbach; U.S. Pat. No. 6,045,488 to Eschenbach; U.S. Pat. No. 6,077,196 to Eschenbach; U.S. Pat. No. 6,077,198 to Eschenbach; U.S. Pat. No. 6,090,013 to Eschenbach; U.S. Pat. No. 6,090,014 to Eschenbach; U.S. Pat. No. 6,142,915 to Eschenbach; U.S. Pat. No. 6,168,552 to Eschenbach; U.S. Pat. No. 6,210,305 to Eschenbach; U.S. Pat. No. 6,361,476 to Eschenbach; U.S. Pat. No. 6,409,632 to Eschenbach; U.S. Pat. No. 6,422,976 to Eschenbach; U.S. Pat. No. 6,422,977 to Eschenbach; U.S. Pat. No. 6,436,007 to Eschenbach; U.S. Pat. No. 6,440,042 to Eschenbach; U.S. Pat. No. 6,482,132 to Eschenbach; and U.S. Pat. No. 6,612,969 to Eschenbach).
Elliptical trainers are widely available in fitness centers as well as many healthcare and home settings. As currently designed, elliptical trainers resist movements for individuals with adequate strength who are attempting to further increase strength/endurance. They do not, yet, have the capacity to adapt to and assist movements for the people with weakness, joint pain, or movement initiation problems. The impact of this limitation is evident in individuals with physical limitations. Many who have a stroke, Parkinson's disease, arthritis, or total joint replacement (with disuse weakness) are unable to initiate or sustain exercise on elliptical trainers unless the clinician provides physical assistance to move the pedals. Once the required assistance is provided, many like the exercise due to its similarity to walking, the smoothness of movement, and opportunity for incorporating trunk and arms into the activity. The similarity to walking of movement patterns and muscle demands while exercising on an elliptical trainer suggests that beyond serving as an exercise tool, elliptical training can help people regain the strength and flexibility required for walking. For example, calf weakness, a common finding in older de-conditioned adults and individuals who have experienced a stroke, limits walking speed by reducing their ability to take steps of adequate length. The elliptical trainer requires calf muscle activity to stabilize the lower leg, particularly as the leg moves into a trailing limb posture. Joint and muscle tightness in persons with hip joint osteoarthritis or those who spend much of their day sitting in a wheelchair contributes to an excessively flexed (bent) posture while walking, which increases muscular demand and slows walking speed. Elliptical trainers with a moveable step length could be used therapeutically to provide a gentle repetitive stretch to tight muscles at the hip during training. A notable difference between elliptical training and walking is that both limbs stay in contact with the support surface during elliptical training, whereas with walking, there are periods when body weight is supported by only one leg. The constant contact of both feet with the support surface during elliptical training reduces the jarring forces associated with repeatedly loading the limb during each step of walking. This could be beneficial for individuals with painful joints.
The physically limited or rehabilitating users experience several difficulties while accessing and positioning themselves on an elliptical trainer. The difficulties are faced because of the potential muscle atrophy, joint stiffening, and general loss of balance and coordination that many rehabilitating individuals are challenged with. Therefore, at times it's difficult for the patients to maintain their posture and positioning on training devices like an elliptical trainer. In addition to the need for tools to help individuals with disabilities regain their walking function in the clinical setting, there also is a need for accessible and appropriately challenging exercise equipment to address cardiovascular and walking function following discharge from therapy programs.